CHICAGO --Chicago Police Supt. Eddie Johnson announced that all of Chicago’s 22 police districts will get new body cameras within the next two years.

"They have served as a building block of public trust and accountability," Johnson said at a news conference Sunday.

The number of cameras will increase to about 7,000, making the CPD the largest camera-wearing force in the country.

Police demonstrated the square-shaped HD cameras. Each can store up to 70 hours of footage, which will routinely be uploaded.

The cameras are simple to operate --a double-tap to star and a single tap to stop.

"It’s not real complicated, but you still have to become familiar with using it on a daily basis," Johnson said.

But there are serious questions about whether officers will use them properly after a police officer shot and killed 18-year-old car theft suspect Paul O’Neal. The officer was wearing a body camera, but it was not recording at the time of the shooting.

Johnson says in general cops will be required to on the cameras once they respond to a call or engage with the public, but he says his department is reviewing best practices from around the country.

Ald. Emma Mitts, 37th Ward, says footage in questionable shootings should be released to the public.

"We have a lot of good police officers out here, we have some that are bad and that’s why we are here today doing this because of bad cops," Mitts said.

Chief of Patrol Fred Waller says there will be a learning curve for cops using new technology.

"It’s going to take a little time for the officers to get acclimated to using the cameras," Waller said.

Johnson says the expansion will cost $8 million and be paid for with city funding and grants.

Additionally, the department has also started holding classes in "de-escalation" procedures. The hope is that it will reduce the number of police shootings.

Classes are going on six days a week and the department hopes to train thousands of officers within the first year. So far, more than 200 officers have taken the training class.